import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';

class LoginForm extends StatefulWidget {
  _LoginPageState createState() {
    return _LoginPageState();
  }
}

class _LoginPageState  extends State<LoginForm> {
  /*
   * TextEditingController 用来操作 TextFieId
   * 1. 为绑定的输入框 TextFieId 预设内容
   * 2. 获取 TextFieId 中输入的内容
   * 3. 监听文字输入变化与焦点变化
   */
  TextEditingController _userNameEditController;
  TextEditingController _pwdEditController;

  final FocusNode _userNameFocusNode = FocusNode();
  final FocusNode _pwdFocusNode = FocusNode();

  @override
  void initState() {
    super.initState();

    _pwdEditController = TextEditingController();
    _userNameEditController = TextEditingController();

    _pwdEditController.addListener(() => setState(() => {}));
    _userNameEditController.addListener(() => setState(() => {}));
  }

  @override
  // TODO: implement widget
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.blue[400],
        elevation: 0,
      ),
      body: SingleChildScrollView(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            buildTopWidget(context),
            SizedBox(height: 80,),
            buildEditWidget(context)
          ],
        ),
      ),
    );
  }

  // 头部
  Widget buildTopWidget(BuildContext context) {
    double height = 200.0;
    double width = MediaQuery.of(context).size.width;
    return Container(
      width: width,
      height: height,
      color: Colors.blue[400],
      child: Stack(
        overflow: Overflow.visible,
        children: <Widget>[
          Positioned(
            left: (width - 90) / 2.0,
            top: height - 45,
            child: Container(
              width: 90.0,
              height: 90.0,
              decoration: BoxDecoration(
                boxShadow: [
                  BoxShadow(color: Theme.of(context).cardColor, blurRadius: 4.0)
                ],
                shape: BoxShape.circle,
                image: DecorationImage(
                  fit: BoxFit.cover,
                  image: NetworkImage(
                    'https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1569298229946&di=ea4ffb2b140ef40035772bbcee7bbdd5&imgtype=0&src=http%3A%2F%2Fcimg2.163.com%2Fcatchimg%2F20090909%2F8112139_3.jpg'
                  )
                )
              ),
            ),
          )
        ],
      ),
    );
  }

  Widget buildEditWidget(BuildContext context) {
    return Container(
      margin: EdgeInsets.only(left: 15, right: 15),
      child: Column(
        children: <Widget>[
          buildLoginNameTextField(),
          SizedBox(height: 20.0,),
          buildPwdTextField(),
          buildLoginButton(),
        ],
      ),
    );
  }

  // 用户名文本框
  Widget buildLoginNameTextField() {
    return Container(
      height: 40,
      decoration: BoxDecoration(
        color: Colors.grey[200],
        borderRadius: BorderRadius.all(Radius.circular(20.0)),
      ),
      child: Stack(
        children: <Widget>[
          Positioned(
            left: 16,
            top: 11,
            width: 18,
            height: 18,
            child: Text('1'),
          ),
          Positioned(
            left: 45,
            top: 10,
            bottom: 10,
            width: 1,
            child: Container(
              color: Colors.black,
            ),
          ),
          Positioned(
            left: 55,
            right: 10,
            top: 10,
            height: 30,
            child: TextField(
              controller: _userNameEditController,
              focusNode: _userNameFocusNode,
              decoration: InputDecoration(
                hintText: '请输入用户名',
                border: InputBorder.none
              ),
              style: TextStyle(
                fontSize: 14
              ),
            ),
          )
        ],
      ),
    );
  }

  // 密码
  Widget buildPwdTextField() {
    return Container(
      height: 40,
      decoration: BoxDecoration(
        color: Colors.grey[200],
        borderRadius: BorderRadius.all(Radius.circular(20.0))
      ),
      child: Stack(
        children: <Widget>[
          Positioned(
            left: 16,
            top: 11,
            width: 18,
            height: 18,
            child: Text('2'),
          ),
          Positioned(
            left: 45,
            top: 10,
            bottom: 10,
            width: 1,
            child: Container(
              color: Colors.black,
            ),
          ),
          Positioned(
            left: 55,
            right: 10,
            top: 5,
            height: 30,
            child: TextField(
              controller: _pwdEditController,
              focusNode: _pwdFocusNode,
              decoration: InputDecoration(
                hintText: '请输入密码',
                border: InputBorder.none
              ),
              style: TextStyle(
                fontSize: 14,
              ),
              obscureText: true,
            ),
          )
        ],
      ),
    );
  }

  // 登陆按钮
  Widget buildLoginButton() {
    return Container(
      margin: EdgeInsets.only(top: 40, left: 10, right: 10),
      padding: EdgeInsets.all(0),
      width: MediaQuery.of(context).size.width - 20,
      height: 40,
      child: FlatButton(
        onPressed: () {
          if (checkInput()) {
            Fluttertoast.showToast(
                msg: '登录成功',
                gravity: ToastGravity.CENTER,
                timeInSecForIosWeb: 2,
                textColor: Colors.white,
                fontSize: 14.0
            );
          }
        },
        child: Text('登录'),
        color: Colors.blue[400],
        textColor: Colors.white,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.all(Radius.circular(20.0))
        ),
      ),
    );
  }

  bool checkInput() {
    if (_userNameEditController.text.length == 0) {
      Fluttertoast.showToast(
        msg: '请输入用户名',
        gravity: ToastGravity.CENTER,
        timeInSecForIosWeb: 2,
        backgroundColor: 	Colors.black,
        textColor: Colors.white,
        fontSize: 14.0
      );
      return false;
    } else if (_pwdEditController.text.length == 0) {
      Fluttertoast.showToast(
          msg: '请输入密码',
          gravity: ToastGravity.CENTER,
          timeInSecForIosWeb: 2,
          backgroundColor: 	Colors.white,
          textColor: Colors.black,
          fontSize: 14.0
      );
      return false;
    }
    return true;
  }

}


